Carrier Transport at Metal/Amorphous Hafnium–Indium–Zinc Oxide Interfaces

Kim, Seongjun; Gil, Youngun; Choi, Youngran; Kim, Kyoung-Kook; Woo, Han Young; Son, Byoungchul; Choi, Chel‐Jong; Kim, Hyunsoo

doi:10.1021/acsami.5b06223

Cited by 12 publications

(7 citation statements)

References 53 publications

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“…Amorphous and polycrystalline mixed-metal oxides are employed in applications that range from thin-film transistors − and solar cells, , to catalysts for reactions including hydrocarbon oxidation, − hydrogen production via water-splitting, and oxygenate reforming. − The versatility of mixed-metal oxide materials is due to their wide range of electronic properties, which depend on chemical composition and physical structure (e.g., crystalline vs amorphous). For example, the band gap of bismuth-containing mixed-transition-metal oxides, used for oxidation catalysis, varies based on the identity of the transition metal(s) due to the dependence of the lowest unoccupied energy levels on empty d-orbitals .…”

Section: Introductionmentioning

confidence: 99%

Transition-Metal-Incorporated Aluminum Oxide Thin Films: Toward Electronic Structure Design in Amorphous Mixed-Metal Oxides

et al. 2018

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Amorphous metal oxides have numerous applications spanning from electronics to catalysis. The ability to rationally design the electronic structure of such materials would thus have significant impact. Previous work has shown that the amorphous structure allows for uniformly incorporating a large number of different metal cations into ultrasmooth thin films. Here we investigate how the atomic structure, electronic structure, and optical absorption properties of amorphous aluminum oxide (a-Al 2 O 3 ) thin films are modulated when metal cations of V, Cr, Mn, Fe, Co, Ni, Cu, Zn, or Ga are added to form M y Al 1−y O x where y varies from 0.1 to 0.7. We use X-ray absorption spectroscopy (XAS) to analyze oxidation state and local bonding around the incorporated cations (e.g., coordination number), valence-band X-ray photoelectron spectroscopy (VB-XPS) to assess the impact of the cations on the valence band electronic structure, and optical absorption spectroscopy to assess the presence and energies of new unoccupied electronic states. Cations with partially filled d-orbitals (e.g., Fe 3+ , Cr 3+ , Co 2+ , Ni 2+ , Cu 2+ , etc.) add filled 3d electronic states at the valence band edge of a-Al 2 O 3 as well as unfilled 3d electronic states within the a-Al 2 O 3 band gap. Cations with the d 10 electronic configuration, such as Zn 2+ and Ga 3+ , introduce filled 3d electronic states at energies well below the valence band edge in addition to new unfilled electronic states in the a-Al 2 O 3 band gap. Cations with unfilled d-orbitals (e.g., those with a d 0 configuration such as V 5+ and Cr 6+ ) do not modify the valence band of a-Al 2 O 3 , but affect the optical properties by inserting unfilled 3d electronic states within the band gap. These results provide guidance for the rational design of the electronic structure of amorphous mixed-metal oxides.

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Section: Introductionmentioning

confidence: 99%

Transition-Metal-Incorporated Aluminum Oxide Thin Films: Toward Electronic Structure Design in Amorphous Mixed-Metal Oxides

et al. 2018

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“…Angle-resolved HAXPES analysis revealed that V O in IGZO:H was much lower than that in IGZO, especially in the region near the film surface (Figure e). Both the increase of ϕ b and the decrease of V O at the Ag x O/IGZO:H interface reduce the tunneling current through the junction barrier due to trap-assisted tunneling. ,,, Moreover, the HAXPES analysis also revealed that the density of near-CBM states in IGZO:H was lower than that in IGZO after annealing at a T ann of 150 °C. The reduction of near-CBM states in IGZO:H also contributed to reduce the tunneling current in the SDs.…”

Section: Resultsmentioning

confidence: 98%

“…Additionally, oxygen-poor regions are formed by the reduction of IGZO when a metal comes in contact with it . These surface and interface defect states increase the carrier concentration of IGZO and lead to the ohmic behavior . This is why the AOS-based SDs show mostly ohmic or near-ohmic, independent of the metal used .…”

Section: Introductionmentioning

confidence: 99%

Record-High-Performance Hydrogenated In–Ga–Zn–O Flexible Schottky Diodes

Magari

Aman

Koretomo

et al. 2020

ACS Appl. Mater. Interfaces

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High-performance In–Ga–Zn–O (IGZO) Schottky diodes (SDs) were fabricated using hydrogenated IGZO (IGZO:H) at a maximum process temperature of 150 °C. IGZO:H was prepared by Ar + O2 + H2 sputtering. IGZO:H SDs on a glass substrate exhibited superior electrical properties with a very high rectification ratio of 3.8 × 1010, an extremely large Schottky barrier height of 1.17 eV, and a low ideality factor of 1.07. It was confirmed that the hydrogen incorporated during IGZO:H deposition increased the band gap energy from 3.02 eV (IGZO) to 3.29 eV (IGZO:H). Thus, it was considered that the increase in band gap energy (decrease in electron affinity) of IGZO:H contributed to the increase in the Schottky barrier height of the SDs. Angle-resolved hard X-ray photoelectron spectroscopy analysis revealed that oxygen vacancies in IGZO:H were much fewer than those in IGZO, especially in the region near the film surface. Moreover, it was found that the density of near-conduction band minimum states in IGZO:H was lower than that in IGZO. Therefore, IGZO:H played a key role in improving the Schottky interface quality, namely, the increase of Schottky barrier height, decrease of oxygen vacancies, and reduction of near-conduction band minimum states. Finally, we fabricated a flexible IGZO:H SD on a poly(ethylene naphthalate) substrate, and it exhibited record electrical properties with a rectification ratio of 1.7 × 109, Schottky barrier height of 1.12 eV, and ideality factor of 1.10. To the best of our knowledge, both the IGZO:H SDs formed on glass and poly(ethylene naphthalate) substrates achieved the best performance among the IGZO SDs reported to date. The proposed method successfully demonstrated great potential for future flexible electronic applications.

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“…Inorganic–organic halide perovskites exhibit intrinsic properties, such as appropriate electronic structures and small exciton binding energy, [ 1–8 ] making it an attractive absorber material in photovoltaics. Low fabrication cost and high efficiencies (currently certified as 25.5% [ 9 ] ) of perovskite solar cells (PSCs) make it promising for commercialization as either single‐junction devices or in tandems with lower bandgap absorber solar cells, including silicon, chalcogenides, and tin‐related materials.…”

Section: Figurementioning

confidence: 99%

Copper Oxide Buffer Layers by Pulsed‐Chemical Vapor Deposition for Semitransparent Perovskite Solar Cells

Eom

Kim

Agbenyeke

et al. 2020

Adv Materials Inter

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In semitransparent perovskite solar cells with n–i–p configuration, thermal evaporation is the common method to deposit the sputter buffer material, such as molybdenum oxide and tungsten oxide. Buffer layers are especially necessary when using organic hole transporting layers, as they are more susceptible to get damaged when sputtering the top transparent conducting oxide. However, there is a limited selection of possible materials and limited control of the materials properties by thermal evaporation, which leads to inefficient protection against sputtering and poor air stability. While there have been well‐established buffer layers by atomic layer deposition, including tin oxide, for p–i–n structured semitransparent perovskite solar cells, this is not the case for n–i–p structured devices. Here, copper oxide is demonstrated by pulsed‐chemical vapor deposition incorporated into perovskite solar cells for the sputter buffer layer, which result in stable encapsulated semitransparent devices maintaining over 95% of the maximum efficiency under AM 1.5 G at maximum power point tracking for 150 h without any temperature control.

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Carrier Transport at Metal/Amorphous Hafnium–Indium–Zinc Oxide Interfaces

Cited by 12 publications

References 53 publications

Transition-Metal-Incorporated Aluminum Oxide Thin Films: Toward Electronic Structure Design in Amorphous Mixed-Metal Oxides

Transition-Metal-Incorporated Aluminum Oxide Thin Films: Toward Electronic Structure Design in Amorphous Mixed-Metal Oxides

Record-High-Performance Hydrogenated In–Ga–Zn–O Flexible Schottky Diodes

Copper Oxide Buffer Layers by Pulsed‐Chemical Vapor Deposition for Semitransparent Perovskite Solar Cells

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